Discharge tube display



Aug 29, 1933.

F. HOTCHNER DISCHARGE TUBE DISPLAY 5 Sheets-Sheet 1 Filed Oct. 4, 1928 lium H II I [1 II-Ill I ii In INVENTOR W Aug'. 29, 1933. F. HOTCHNER DISCHARGE TUBE DISPLAY 3 Sheets-Sheet 2 Filed 0ct 4, 1928 zw s 6 m $.33 a, g \V ifi x? y 5 MI" I a l 8 2 a n h v 4 Q q 2/ w 5.54. I 8 6 w 3 IN VEN TOR Aug. 29, 1933. F. HOTCHNER' 1,924,497

DISCHARGE TUBE DISPLAY Filed 0013. 4, 1928 3 Sheets-Sheet 3 /NVEN TOR red Patented Aug. 29, 1933 UNITED STATES PATENT OFFICE 6 Claims.

This invention relates to a discharge tube display and has for its .object to produce a display such as an electric sign in which the lights are discharge tubes, a number of such tubes being 5 flashed in any desired order, making use or" a single transformer,

Heretofore, in flashing discharge tubes the common method has been to connect each tube, or set of tubes that are to be flashed together, series with the secondary of a transformer and to connect the primary of the transformer to a low voltage flasher. To the best of my knowledge no commercially acceptable device has been v available for the purpose of flashing series connected tubes on the high voltage side of a transformer. Consequently it has been necessary to use a minimum of as many transformers as the number of such above-described flashing units in. the display. A standard transformer was used for each unit of the first size above that required by the size of the unit. As there are very few sizes of transformers available, and the sizes oi the tubes vary greatly, itfiollows that in many cases a considerable surplus of transformer capacity must be used above that which would be required were all of the tubing connected together on a single transformer. A further object of this invention, therefore, is to provide means of operatin from a single transformer a number of tubes up to the total footage of which the transformer is capable oi lighting.

Another object is to flash a number of tubes operating from a single transformer and to light them to a uniform intensity regardless of total footage of tubing in circuit at any "instant.

As it might in some cases be desirable to'build a single tube providedwith a number or electrodes thruout its length and to dash various sec tions of such a tube, another object is to provide means to flash various lengths of such a tube and always light them uniformly regardless oi the number of sections in circuit at any time.

The flashing of discharge tubes is attended by -problems entirely different than those met in flashing incandescent lamps. Unlike a lamp which possesses in a measurable degree resistance only, the phenomena in a discharge tube is extremely complicated, it is affected by many outside influences and the characteristics are constantly changing over the period of the life of the tube and during the cycle oi current changes.

The tubes are inherently non-sel=regi1lating, that is, it is necessary that the flow of current thru the tubes must be controlled by means other than the tubes themselves. They also affect the flow of current as they possess capacity in varying degrees, often display a pinch efiect and read ily oscillate with the connected apparatus when inductance is present.

Another factor of importance is the ability of discharge tubes to light by excitation from a single wire connected to a source of current. The degree of illumination is entirely out of proportion with what might be expected by calculation of corona loss, insulation leakage and the capacity of the system. It might more easily be accounted for by regarding the tubes as energy receivers at increased frequency. My theory to account for the relatively large amount of illumination so produced is as follows. A certain amount is produced by leakage' current thru the walls of the tube itself acting as the dielectric of a condenser, the current being dissipated into the air from foreign substances on the outside of the tube acting as a plate. The body of the gas itself apparently is capable of holding an amount of energy in addition to the capacity efiect'in the tube, this energy being absorbed in the displacing of large numbers of electrons in their orbits. "it is conceivable also that a packing of electrons into the body of gas takes place. These effects are cumulative and result in a high oscillation taking place in connection with whatever inductance might be in the circuit. Thus, ordinarily, discharge tube is not completely extinguished disconnecting one terminal from the trans former.

is this tendency of tubes lighting out or installation. In order to overcome the ditficulty, 9

I have made use of another phenomena of discharge tubes which is, the time lag of illumination. factors, but largely by the residual ionization. This effect is not noticed upon the application of high voltages to tubes, but is apparent with the application of a voltage approximating that mini mum required to illuminate the tube atcomrner-= cial frequencyand on the application of high fro guency current. An appreciable time elapses be-= fore the tubes light. Apparently in the absence of a high voltage an appreciable amount of residual ionization must be present for the tubes to thus light. .By deenerglzing the entire system for a period of time suflicient to allow most of till This'is determined again by a number of I the residual ionization to disappear, switching the connections during the dark period, and again energizing the system, I have succeeded in flashing a series of discharge tubes with a single terminal flashing system and still prevent the tubes from lighting out of time. I have also found that this dark period can be reduced so that it is not perceptible to the eye and very. pleasing effects can be secured. A further object of this invention is, therefore, to provide means of switching or flashing the high voltage circuits of a discharge tube display without the necessity of switching both wires leading to each individual unit. I

It is a further object of this invention to provide menas to avoid the losses due to the energization current of the transformer during the periods when the display is all dark. In addition to the transformer losses there are'losses from leakage and corona on the high voltage side which are increased when the tubes are disconnected. By deenergizing the transformer during the all dark periods both of these losses are avoided and the strain on the insulation is also lessened thereby reducing .the cost of maintenance.

This invention is distinguished from previous methods offlashing discharge tube signs in that instead of resorting to the expedient of a number of transformers or cumbersome high-voltage switches, I have provided an apparatus for switching the connections to a number of discharge tubes operating from a single transformer with a device on the primary circuit to make and break the circuit. The apparatus is therefore entirely relieved of the duty of breaking a high voltage are and need only be designed to meet good mechanical practice and-proper insulation clearances. This device is, as described in detail below; in the form of an oil switch. The

clearance distance between the contacts over which the voltage of the transformer is applied or any portion of the voltage is applied during the operation is reduced to a very small figure due to the use of 011 instead .of air for an insulator. No allowance need be made for depreciation of the oil by arc-breaking service. If this same type of machine were to be made with air as an insulator instead of oil a clearance of several inches would be required between the high voltage contacts where a fraction-of an inch here sufiices. The difference in an oil switch made in the manner and for the duty I have given it, and the manner in which it would have to be built were it to perform high voltage arc-breaking service is so great as to become apparent to the most casual inspection. When an oilswitch performs arc-breaking service the contacts must be heavy enough to stand the rise .in temperature and rapid depreciation in service. The oil is carbonized by the arc and hence the clearances must be enormously increased as the insulation value of the oil is impaired. The contacts must be frequently renewed and the oil replaced periodically. Ventilation must be provided out of the oil chamber to release the gases generated and the installation must be made much more expensive to meet the fire hazard of an oil switch. It is an object of this invention; therefore, to provide an oil switch which will becompact and light in construction, that will not depreciate rapidly, that will not release gases and will not be a fire hazard.

A further object is to provide a flasher which will flash a number of discharge tubes without flicker or lag perceptible to the eye between the flashing periods.

indicated by the numeral 21.

Another object is to provide an oil switch having a number of stationary contacts and a revolving distributor contact, in which it is not necessary to carry current thru the shaft of the revolving contact element. This is of importance in this work due to the difliculty of insulating the high voltage and the hazard that would be present were collector brushes to be used outside of the oil chamber.

Another object is to provide a means for flashing a discharge tube circuit in such manner as to minimize the tendency to oscillations.

The above and other objects are accomplished by instrumentalities pointed out in the following specification.

The invention is clearly deflned in the claims.

A satisfactory embodiment of the invention is illustrated in the accompanying drawings but there are many modifications possible in the construction illustrated within the purview of the claims.

Figure 1 is a plan view of a flasher made according to this invention for the purpose of giving an effect known as a four point speller.

Figure 2 is a sectional elevation of the machine shown in Fig. 1.

Figures 3, 4, 5, 6, 7, 8 and 9 are perspective views of various parts of the machine to clearly show the construction.

Figure 10 is a perspective view of the oil switch contact assembly.

Figure 11 is a perspective view of the complete machine. I

Figure 12 is a diagram of the electrical connections of a complete display made according to this invention in which each letter of the display comprises a separate tube.

Figure 13 is a diagram of the electrical connections of a complete display made according to this invention in which a single tube divided into sections by electrodes is used.

In the drawings the same numerals are used to indicate the same part thruout all the views.

Numeral 1, Fig. 2, indicates the flasher which is composed of four major assemblies which are; the oil switch '2, the driving mechanism 3; the thermostatic timer 4 and the primary contactor 5.

The oil switch 2 has a tank 6 which is also the base of the machine, the gasket 7, the cover 8,

the stationary electrodes, 9, 10, 11, 12, 13, 14 and 15, the rotating electrode 16, the distributing brush 17 and the feed'brush 18. Suitable screws such as shown by 19 and 20 hold the cover. tank and gasket together.

The stationary electrodes are formed as hollow insulating tubes as shown in Fig. 2 and Fig. 8, Each tube having a shoulder 22 which is pulled up, against the gasket 7 by the nut 23 on the threaded end 24. The wire 25 extends thru the tube and is soldered into the metallic plug 26 in the other end. The contact"27, and in the case of the electrode 9, also the feed brush 18, is held to the plug 26 by the screw 28. This construction provides a simple terminal for the wires, a rigid contact and an oil-proof connection.

The rotating electrode 16, shown in Fig. 9, consists of an insulating block 29 which is fastened to the shaft 30 by the pin 31. The distributing brush 17 is fastened to the block 29 by thescrews 32 and 33.

The distributing brush 1'! is shown in Fig. 2 in contact with the electrode 9, and in Fig. 10 in contact with the electrode 12. This construction has the advantage of making a unit of the entire high-voltage contacting system, which can be assembled and adjusted before closing the machine, and can be removed from the machine for inspection at any time without disturbing the relation of the parts. By thus using one of the electrodes for the feed it is possible to avoid open contacts outside of the oil chamber and to make the machine simple and compact. The feed contact corresponding to electrode 9 represents a dark period in the operation of the display.

The driving mechanism 3 consists of the magnet coil 34, the iron yokes 35 and 36, the armature assembly 37, Fig. 4, the stop pawl assembly 38, Fig. 5, the support 39, Fig. '7, the spiral spring 40, Fig. 7, and the ratchet 47, Fig. 3.

The armature assembly 3'7 consists of the rocking sleeve 41 to which the armature bars 42 and 43 are rigidly fastened. The rocking arms 44 and 45 are rigidly fastened to the sleeve 41 by the pin 46. The arm 44 carries the stop-pawl cam 49 which has a downward extending portion 49 which strikes the yoke 35 and thereby limits the movement of the armature assembly in clockwise rotation. The arm 45 carries the pivot 50 on which the drive pawl 51 turns and the boss 52 to which the flat spring 53 is fastened by means of the rivet 5%.

The stop pawl assembly 38 consists of the frame 55 which is fastened to the yoke 35 by the screws 56 and 57. It has a vertical pivot 58 on which the stop pawl 59 turns, and the boss 60 to which the flat spring 61 is fastened by means of the rivet 62.

The support 39 consists of the collar 63 and the arms 164 and 165 which support the driving mechanism and are fastened to the yokes 35 and 36 bythe bolts 54, 65, 66 and 6'7. The collar 63 is secured to the cover 8 by the pins 68 and 69. The arm has a pin 70 which holds one end of 'the flat spiral spring 40. The other end of the spring 71 is fastened to the armature bar 42 by the screw '72. p

The shaft 30 has the tight collar '73 which bears against the gasket '7, and the tight collar '74:. The armature assembly turns free on the shaft.

The ratchet 4'7 is tight to the shaft.

The thermostatic timer 4 consists of an in sulating base '75 to which is secured the timing element '76. The function of the timer is to energize and deenergize the magnet periodically. Any one of many common types of timers may be used for this purpose.

The primary contactor 5 consists of the pivot post '77, the rocker arm 76, the spring '79, the in sulating base 80, the stationary contact 81 and the moving contact 82. On the ratchet 4'7 are the projections 82, 83, 84, 85 and 86.

The diagram in Fig. 12 illustrates one type of display that may be constructed according to the disclosure of the specification. This display is of the type known as speller in which one letter or one word is flashed on at a time until the display is all lighted, all are then extinguished, all are flashed on again, all are then flashed off and the operation repeated continuously. Many other effects can be secured by other arrangements of contacts and circuits.

8'7, 88, 89 and 90 are discharge tubes, each being provided with two electrode terminals. The transformer 91 hasthe low-voltage primary coil 92 and the'high-voltage secondary coil 93. The terminal 94 of the primary coil 92 is con nected to one supply wire 95 and .the other terminal 96 is connected to the other supply wire 97 thru the primary contactor 5. One terminal 98 of the high-voltage coil 93 is connected to one terminal 99 of the tube 8'7.

The other terminal 100- is connected to the electrode 9 of the oil switch 2. The current is carried to the revolving electrode 16 by the feed brush 18 from the electrode 9 and is distributed to the other electrodes by the distributor brush 1'7.

The electrode 101 on the tube 8'7 and the elec- U trode 102 on the tube 88 are connected together point the entire display is lighted. At the point a corresponding to the electrode 14 the display is dark as there is no connection to this electrode. Electrodes 13 and 15 are connected together and therefore the display is again entirely lighted when the distributor brush reaches this point, and is again dark when the distributor brush reaches electrode 9.

The diagram in Fig. 13 illustrates a similar dis play to that shown in Fig. 12 with the exception that the entire word represented by the tubing is" formed of a single tube divided into sections cor responding to the letters by electrodes. The portions of the tubing which is ordinarily formed to double back of itself for the sake of appearances is here illustrated as lying in a single plane. It is to be understood that this is merely for the purpose of illustration and the tubing may be formed in'any desired manner. The portions of the tubing not actually included in the individual letters may be rendered opaque in any known manner. All elements in this diagram corresponding to those in Fig. 12 are indicated by the same numeral with the exception of the parts of the tube. The tube is indicated by numeral 120, and is divided into the sections 121, 122, 123 and 124 by the electrodes. Electrodes 125 and 126 at the ends correspond to electrodes 99 and 107 in Fig. 12. Likewise electrodes 127, 123 and 129, intermediate of the ends correspond to elec-- trodes l0l102 and 103-104 and -406 in Fig. 12. The operation of the device is the same in both cases.

The operation of the machine is as follows. The thermostatic timer energizes the coil periodically. A magnetic field is set up thru the iron yokes and the armature bars move to close the fields. The pawl 51 drives the ratchet, shaft and movable parts of the oil switch counter-clockwise one seventh of a revolution. As the rocker arm 44 draws the cam 48 away from the pawl 59, the pawl 59 is allowed to move into position to stop the ratchet tooth that is being driven by the pawl 51. The armature is thus brought to a definite point and stopped. The distributor brush is moved rapidly from one point to the next with each movement of the armature counterclock- 1 wise, there being just sufficient friction on the contacts to prevent the shaft from turning on the return movement of the armature. If desired another pawl can be used for this purpose.

The length of time that the thermostat holds the magnet in circuit is of no importance as the rise ratchet lift the rocker arm 78 and close the circuit to the primary of the transformer. These projections are positioned to be under the rocker arm when the oil switch contacts are centered..

6 The parts are adjusted so that the primary contact is open before the oil switch contacts have parted and the primary is closed after the oil switch contacts have met. There are no projections at the points corresponding to the all off" periods and the transformer is dead at those positions. Thus the oil switch is relieved of all arc-breaking service.

It is of the utmost importance that the movement from one position to the next be made very rapidly in order that no objectionable flicker will be noticed in the display. This is possible in this construction as all of the moving parts can be made very light and the lever arms short. The clearances in the oil switch can be very close since there is no carbonization of the oil and when desired the machine can be built with numerous contact points.

The primary contactor serves several purposes. The first is to deenergize the transformer before the oil switch contacts part in order to relieve the oil switch of arc-breaking service. The next is to deenergize the transformer during the all off periods in order to conserve current, prevent glow in the tubes from one terminal excitation and to relieve the strain on the insulation. Its most important function is to provide a period during which the residual ionization falls to a low value or disappears between the illumination periods. This period might be so short as not to be-noticed at all in the operation .of the display, but is absolutely necessary for successful operation. A simple test with' the device illustrated demonstrates the principle.

If the flasher is stopped in the all ofi position and the primary contactor is closed, practically the entire display becomes visible by energy taken from the terminal 98 of the transformer. The nature of the light and the degree of illumination clearly evidences the existence of high frequency currents. The light diminishes towards the electrode 10"! in a fairly uniform manner. If now the flasher is operated in the usual manner and stopped at any position, with part of the tubes lighted and part of the tubes dark, no glow at 50 all will extend into the dark tubes altho oneterminal is still connected to a charged wire. It is to be noted that at times when the switch closes at a stage in the operation of the-device in which some of the tubes are dark,.a very light and short flash is to be seen in the dark tube. However,

after this short flash in the dark tube or tubes;-

when it does occur the tubes so affected are completely dark and show no evidence of surges or high frequency currents. This flash is so short as to be almost imperceptible and appears to be a one half cycle surge. That is to say, the dark tubes having had a chanceto become thoroughly deionized during the switching period have developed a resistance to the setting up of current flow which is not broken down by this initial surge. That it is not sustained is due to the fact that the tubes which are in circuit are intensively ionized each half cycle and carry suincient unrecombined ions thru the zero position to prevent the current taking any other than the desired path, whereas the tubes that are out of circuit have lost most of their iarization during the switching onerltim and thereafter 'haveacompleteonel'nltqdepedoddurlngeach cycle to allow an m the to surges to diaappear; Thus this initial surge when it does occur does not tend to set up oscillations in the dark tubes. It is evidently cut short by the initiation of flow in the tubes that are to be lighted, and, of course, cannot occur on the following half cycle as the lighted tubes are new highly ionized and more readily respond to the rising voltage. In working with tubes in the laboratory experimentally, one can frequently observeby impressing voltagesacross tubes barely sufficient to light them that there is a resistance to the initial ignition of a tubethat has been dark for a period of time that is greater than the resistance to break down upon each half cycle of alternating current voltage.

In order to illuminate the tubes to the same degree of intensity regardless of the total footage of tubing in circuit, I make use of a transformer of a high reactance. A transformer having a power factor of about thirty percent and suflicient voltage to illuminate all of the tubes in the display in series will deliver a current of a sufliciently uniform value regardless of the amount of tubing in the circuit at any instant. What variation does occur is too small to be noticed by the' eye. The new result is thus accomplished of flashing on successive lengths of discharge tubes to the. terminals of a single transformer without interruption of the illumination of the lighted tubes sufiicient to be noticed by the eye and always lighting the tubes to the same intensity regardless of the amount of tubing in he circuit. Various other means are available for this purpose however, notably, a properly designed choke coil either in the primary or the secondary circuit.

Instead of using a number of individual tubes it is possible with my invention to use a single tube with a number of electrodes along the tube. This is an advantage as it is possible thereby to reduce the number of electrodes and otherwise economize on the construction. I

In my copending application, Serial No. 157,333 filed Dec. 27, 1926 entitled Flashing discharge tube signs, I have disclosed and broadly claimed a device of this character to produce animated effects.

'Having thus described my invention and the manner of constructing and using the same, altho without attempting to set forth all of the forms in which it may be made, or all of the modes of its use, I claim:

1. In combination: a luminous display device comprising one or more discharge tubes and divided into series-connectedsections bounded by electrodes; a transformer providing a low voltage primary winding and a high voltage secondary winding; means for connecting said secondary winding in stages to a different group of said electrodes in each stage thus connecting in circuit with said secondary winding a different group of series-connected sections in each stage with a period of time between the successive connections; and means for deenergizing said primary winding immediately before the start of said period of time and for energizing said primary winding immediately after said period of time.

2. In combination: a luminous displaydevice comprising .one or more discharge tubes and divided into series-connected sectiom bounded by electrodes: atramformerpmvidmgahwvoltage prinnry winding and a 11th volt-0e lecmduy wlndin meamfm meofthe terpinch at said may windm tonne of said electrodes; selectameans for lueeesively-emnecting the other terminal of said secondary winding to certain other of said electrodes; and means for deenergizing said primary winding before said selector means changes connections to said electrodes and again energizing said primary winding only after said selector means changes connections to said electrodes.

3. In combination: a luminous display device comprising one or more discharge tubes and divided into series-connected sections bounded by said terminals of said high tension winding to said contact means; advancing means associated with said contact means and moving said contact means successively into contact with said distributor electrodes; and switch means timed by said advancing means for successively energizing and deenergizing said primary winding during the time interval in which said contactmeans is in engagement with each of said distributor electrodes.

4. A method of operating a luminous display, which method includes the steps, in flashing a configuration of one or more discharge tubes divided into sections bounded by electrodes with the ends of each section electrically common to the ends of the adjacent sections all ofthe sections being series-connected, of connecting the secondary coil of a step-up transformer to a pair of electrodes bounding a given number of said sections with a remaining portion of said sections connected to one terminal of said coil by one electrode only, the primary circuit of said transformer being open at the instant of connection of said secondary coil to said group of sections, and thereafter closing said primary circuit to set up a discharge in said sections included between said pair of electrodes and not in said sections connected to said source by one electrode only.

5. A method of operating a luminous display,

which method includes the steps, in flashing a configuration of one or more discharge tubes divided into sections bounded by electrodes with the ends of each section electrically commonto the ends of the adjacent sections all of the sections being series-connected, of establishing a discharge in a portion of said sections by connecting the pair of electrodes bounding said portion to the secondary coil of a step-up transformer with a remaining portion of said sections connected to said coil by one electrode only, opening the primary circuit of said transformer and changing the connections of said secondary coil to said sections to include a different portion of said sections between a pair of connected electrodes with a portion of said sections remaining connected to said secondary coil by one electrode only, and thereafter closing said primary circuit to establish a discharge in the sections bounded by the connected electrodes and not in the remaining sections connected by one electrode only to said source.

6. A method of operating a luminous display, which method includes the steps, in flashing a configuration of one or more discharge tubes divided into sections bounded by electrodes with the ends of each section electrically common to the ends of the adjacent sections all of the sections being series-connected, of establishing a discharge in a portion of said sections by connecting the pair of electrodes bounding said portion to the secondary coil of a step-up transformer witha remaining portion of said sections connected to said secondary coil by one electrode only, opening the primary circuit of said transformer and changing the connections from the secondary coil of the same to said sections to include a different group of said sections in which group remain some of the sections first thus connected to the said secondary coil between bounding electrodes with a remaining portion connected to one terminal of said source of potential by one electrode only, and thereafter closing said primary circuit to establish a discharge in the said sections bounded by the connected electrode and not in the remaining sections connected to said source by one electrode only.

' FRED HOTCI-INER. 

